public class ClassLoaderTest {
    public static void main(String[] args) {
        // 获取系统类加载器
        ClassLoader systemClassLoader = ClassLoader.getSystemClassLoader();
        System.out.println(systemClassLoader);//sun.misc.Launcher$AppClassLoader@18b4aac2

        // 获取其上层：扩展类加载器
        ClassLoader ExtClassLoader = systemClassLoader.getParent();
        System.out.println(ExtClassLoader);//sun.misc.Launcher$ExtClassLoader@1b6d3586

        // 获取其上层：获取不到引导类加载器
        ClassLoader bootstrapClassLoader = ExtClassLoader.getParent();
        System.out.println(bootstrapClassLoader);//null

        // 对于用户自定义来说: 默认使用系统类加载器进行加载
        ClassLoader classLoader = ClassLoaderTest.class.getClassLoader();
        System.out.println(classLoader);//sun.misc.Launcher$AppClassLoader@18b4aac2

        // String类使用引导类加载器进行加载 -------> java的核心类库
        ClassLoader classLoader1 = String.class.getClassLoader();
        System.out.println(classLoader1);//null
    }
}
